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November 18th, 2012, 10:48 AM
#1
Does DefWindowProc while processing WM_ERASEBKGND use update region?
Hi,
I process WM_ERASEBKGND message for WS_CHILD window:
Code:
case WM_ERASEBKGND:
GetUpdateRect(hWnd,&urect,FALSE);
//...........
In urect i always get {0,0,0,0}. That's why I ask: does DefWindowProc while processing WM_ERASEBKGND use update region or erase entire client area?
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November 18th, 2012, 11:02 AM
#2
Re: Does DefWindowProc while processing WM_ERASEBKGND use update region?
Sorry, I was mistaken. In urect there is no always {0,0,0,0}. But my question still in force: Does DefWindowProc while processing WM_ERASEBKGND use update region or erase entire client area?
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November 19th, 2012, 06:56 AM
#3
Re: Does DefWindowProc while processing WM_ERASEBKGND use update region?
I answer my question myself(it was checked) - Yes. But when BeginPaint send WM_ERASEBKGND internally, the update rect is always {0,0,0,0}. Why?
I know that before returning BeginPaint validate the update rect and that's why it is always {0,0,0,0}. But how DefWindowProc or my own code in processing WM_ERASEBKGND message will know update region if GetUpdateRect always return {0,0,0,0}?
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